Restrictor for hydraulic pump



United States Patent O U.S. Cl. 91-49 3 Claims ABSTRACT F THE DISCLOSURE A uid control valve for an automatic reversing piston assembly has the'ow of lluid to one end thereof controlled by a split sleeve which serves also as a bearing for a valve rod.

Brief summary of the invention In U.S. Patent No. 3,218,980 an automatically reversing air operated piston assembly which drives a hydraulic pump is disclosed and claimed. This piston assembly includes a control valve which is seated during the pressure stroke of the piston assembly and unseated at the end of the pressure stroke to allow air pressure to substantially equalize on opposite sides of the piston assembly so that spring pressure can return the piston assembly to its Original position.

Experience with this type of unit has revealed that damage to the control valve may occur due to high force acting on it. It is the purpose of the present invention to provide a means to control the rate of pressure build up on the control valve and thereby eliminate excessive force acting on it. The invention does this by means of a split sleeve or roll pin which is placed in the piston assembly so that it serves as a support sleeve for a tri-p valve thereby further facilitating the operation of the unit.

Description of the drwin-gs FIGURE 1 is -a longitudinal cross-section of lan airhydraulic pump unit according to U.S. Patent No. 3,218,- 980 and embodying the invention;

FIGURE 2 is an enlarged broken away section showmg the piston assembly; and

FIGURE 3 is a cross section along the line 3-3 of FIGURE 2.

Description of the invention The air-hydraulic pumping unit 1 has a casing 3 with an end cap 5 at the air inlet end and an end cap 7 at the .pumped hydraulic fluid outlet end. A reciprocating piston assembly 9 works inside of the cylinder 3 to drive a long pump rod 11 which works inside of the bore 13 of a pump cylinder 15 that supplies hydraulic fluid under pressure to a desired point such as a hydraulic jack. Compresslon spring 17 is based at one end against the end cap 7 and engages the piston assembly 9 to resist its compresslon stroke and act as a resilient means for returning the plston assembly tothe left in FIGURE 1. A cushioning spring 19 is based against the end cap 5 and grips a rubber cushion member 21 at the left end of the piston 9 and acts with the rubber cushion to absorb shock loads o n the piston assembly and the control valve 23 which 1s mounted inside of the :piston assembly.

The piston assembly 9 includes a piston member 25 which engages the inner wall of the sleeve 3 and is sealed to it by a U packing 27. The piston 25 has a central aperture 28 which includes a smaller diameter section 29, an intermediate diameter section 31, and a large diameter section 33, there being a shoulder 35 between the aperture sections 31 and 33. A plug 37 is threaded into one end of the large diameter aperture 33 and is also threaded to one end of the pump plunger 11 as seen at 39 whereby the piston assembly 9 carries and moves the pump plunger 1.1.

3,448,658 Patented June l0, 1969 The control valve 23 is cross shaped in cross-section except for a small diameter land 41 at one end which works in bore 29 and a large diameter land 43 at the other end which works in the "bore 33. Preferably the Ipiston 23 is made of a plastic material and therefore does not have the strength of metal so that control of the forces acting on it is highly desirable. Air pressure from the air inlet line 45 reaches a chamber 49 'at the left end of the piston assembly 9 and therefore acts against the left land 41 of the control valve 23. A packing 47 is attached to the land 41 t0 seal aperture 28 during the pressure stroke of the piston assembly 9. Acting against the right hand end or land 43, which is substantially larger in area than the land 41, is the air pressure in a chamber 51 formed by the inside end of the plug 37 and a packing 53 that is attached to the land 43. In a seated position wherein the valve 23 blocks flow through the aperture 28 the packing 53 engages against a stop face 55 formed on the end of the plug 37. It can be seen that because of the relative areas, an unbalanced high pressure in chamber 51 can cause `the land 43 to strike with great force against the shoulder 35 so that repeated blows might damage the valve 23 at this point, particularly if it is made of plastic material.

Flow of air to the chamber 51 is under the control of a valve member 57 which includes a long stem 59 and an enlarged resilient head 61 which seals off or admits air pressure from chamber 49 to a long bore 63 in the piston 25. A cross passage -65 connects the bore 63 and therefore vthe inlet air pressure chamber 49 to the chamber 51 behind the land 43.

During the pressure stroke of the piston assembly 9 to the right, air pressure in chamber 49 will seat the valve head 61 to block off ow to the chamber 51. This will also force the piston 23 to the position shown wherein it blocks off aperture '28. Bleed holes 67 in the plug 37 permit reduction in volume of the chamber 51 resulting in the seating movement of the control valve 23. With the parts in this position air cannot pass by the piston assembly 9 and which is forced to move to the right in the casing with 4the air in chamber 69, to the right of the piston assembly, escaping through ports 7.1 in the end cap 7. When the compression stroke is substantially complete enough pressure is exerted by trip plate 72 on the right end of the trip valve plunger 59 to retard or stop its motion to the right. Further movement of the piston assembly 9 will therefore result in unseating of the valve -head l61 whereby the pressure in chamber 49 reaches chamber 51. This moves the control valve 23 to the left with respect to the piston 25 so that the small land 41 passes beyond the end 73 of the piston to allow air pressure from chamber 49 to enter the aperture 28 and flow through cross-passage 75 in the :piston 25 to reach the Ichamber 69 to provide pressure conditions causing the piston assembly 9 to be moved to the left.

In order to control the rate at which air pressure enters the chamber 51 a relatively long roll pin or split sleeve 77 is disposed in the bore 63 and it has a longitudinal opening 79 extending along its length through which air can flow from. chamber 49 to the passage 65. This sleeve 77 also serves as a support for the trip valve plunger rod 59 without introducing excessive wear and prevents the long valve from drifting off center to cause a malfunction. Because of the throttling effect of the passage 79 in the split sleeve 77, the tendency for high pressure air in chamber 49 to rush into chamber 51 as it expands in size is prevented and the :pressure in chamber 51 is permitted to drop at the instant the differential valve 23 starts to move. 'Ibis instant pressure drop on the large end 43 reduces the pneumatic force on that end when the valve strikes the shoulder 35 and also makes it easier for the spring and cushion 19 and 21 to push the valve 23 back to its retracted position.

Modifications may be made in the structure illustrated 3 Without departing from the spirit and scope of the invention.

I claim:

1. In a fluid pressure actuated pumping device or the like, a cylinder, `a piston -assembly reciprocating in said cylinder `and including a piston having a rst face at one end exposed to actuating pressure in the cylinder and a second face at the other end exposed to atmospheric pressure, control valve means carried by the piston assembly and including a valve member operative upon unseating to provide for passage of uid pressure from the rst to the second face, said control valve means including a pressure chamber in the ypiston at one end of the valve member for application of pressure on the rrst face to the valve member to cause unseating of the valve member, said piston including an elongated trip valve bore and passage connecting the rst face to said pressure chamber, a long stern valve in said bore having a valve head at the rst face end for controlling admission of pressure on the first face to said bore and passage, said valve having a stern substantially smaller in diameter than said bore so that :pressure fluid can ow along the stem in the bore, and a sleeve in said bore serving as a bushing for the stem and having a restricted area passage along its length to control the rate of pressure flow from the valve head end of the bore to said passage and pressure-chamber.

2. A device as set forth in claim 1 wherein said sleeve comprises a roll pin type split sleeve.

3. A device as set forth in claim 1 wherein said valve member is formed of plastic and is forced against a seat by pressure in said pressure chamber.

References Cited UNITED STATES PATENTS 3,218,980 l1/l965 Arnes 103-50 CARROLL B. DORITY, IR., Primary Examiner.

U.S. Cl. X.R. 

